Parasite Stress, Collectivism, and Human Warfare

Kenneth Letendre, Corey L. Fincher and Randy Thornhill

in The Oxford Handbook of Evolutionary Perspectives on Violence, Homicide, and War

Published in print July 2012 | ISBN: 9780199738403
Published online November 2012 | | DOI:

Series: Oxford Library of Psychology

Parasite Stress, Collectivism, and Human Warfare


We recently proposed a new model to explain cross-national variation in the frequency of intrastate conflict based on the parasite-stress theory of sociality. In regions of high pathogen severity, cultures are characterized by xenophobia and ethnocentrism, which function in the avoidance and management of infectious disease. The xenophobia expressed in environments with high pathogen severity creates barriers to intergroup cooperation. These barriers cause greater poverty in environments with increased pathogen severity, in addition to the direct effects of disease on the human capital that is essential to economic growth. Xenophobic groups in competition for resources are unwilling to resolve this competition through cooperative means, and they are more likely to resort to violent conflict. Here, we extend our findings to other categories of conflict. We discuss the implications of our model to the understanding of human warfare in evolutionary context and to foreign aid directed at reducing poverty and conflict.

Keywords: armed conflict; collectivism-individualism; coups; infectious disease; peace; revolutions

Article.  14899 words. 

Subjects: Psychology ; Social Psychology

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